Asphalt-surfaced roadways are built to facilitate vehicular travel. Depending upon usage density, base conditions, temperature variation, moisture variation, and/or physical age, the surface of the roadways eventually become misshapen, non-planar, unable to support wheel loads, or otherwise unsuitable for vehicular traffic. In order to rehabilitate the roadways for continued vehicular use, spent asphalt is removed in preparation for resurfacing.
Cold planers, sometimes also called road mills or scarifiers, are machines that typically include a frame propelled by tracked drive units. The frame supports an engine, an operator's station, and a milling drum. The milling drum, fitted with cutting tools, is rotated through a suitable interface by the engine to break up the surface of the roadway. The broken up roadway material is deposited by the milling drum onto a lower or primary conveyor for removal from the underside of the machine. The material is then transferred from the primary conveyor onto an upper or secondary conveyor, which transports the material away from the machine and over a nearby haul truck. The material travels up the secondary conveyor and falls off the end into the haul truck for transportation away from the jobsite. An exemplary cold planar having the above-described conveyor system is disclosed in U.S. Pat. No. 6,733,086 of McSharry et al. that issued on May 11, 2004.
In typical cold planers, a speed of the conveyors is controlled manually from inside an operator station. In particular, the primary and secondary conveyors are powered by hydraulic motors that are connected in series to a common pump. And based on operator input, a displacement of the common pump is adjusted. This displacement results in a greater or lesser flow rate of fluid passing through the motors and a corresponding speed increase or decrease in the primary and secondary conveyors.
While effective in some applications, the conveyor system of conventional cold planers may be problematic in other applications. Specifically, there may be situations where the operator desires to change the speed of the secondary conveyor independently from the speed of the primary conveyor. For example, a faster or slower material feed rate from the secondary conveyor into the haul truck may improve truck loading. However, the same change in the speed of the primary conveyor could cause material removal problems, material transfer problems, low efficiency, and/or excessive belt wear.
The conveyor system and cold planer of the present disclosure solve one or more of the problems set forth above and/or other problems in the art.